Methods and apparatus for measuring the melt depth of a substrate during pulsed laser melting are provided. The apparatus can include a heat source, a substrate support with an opening formed therein, and an interferometer positioned to direct coherent radiation toward the toward the substrate support. The method can include positioning the substrate with a first surface in a thermal processing chamber, heating a portion of the first surface with a heat source, directing infrared spectrum radiation at a partially reflective mirror creating control radiation and interference radiation, directing the interference radiation to a melted surface and directing the control radiation to a control surface, and measuring the interference between the reflected radiation. The interference fringe pattern can be used to determine the precise melt depth during the melt process.
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2. The method of claim 1, wherein a plurality of reduced areas of the substrate are concurrently heated by directing focused radiation at each, and the method comprises concurrently determining the depth of the melt interface at each of the plurality of reduced areas.
3. The method of claim 1, wherein the control surface is a mirrored surface.
4. The method of claim 1, wherein the substrate comprises silicon.
5. The method of claim 1, further comprising directing a coherent radiation towards a partially reflective mirror to generate the interference radiation and the control radiation.
6. The method of claim 1, wherein heating the reduced area of the first surface comprises directing a second coherent radiation there towards.
11. The method of claim 10, wherein the mirrored control surface is parallel to a direction of the coherent radiation directed from the coherent radiation source to the partially reflective mirror.
13. The method of claim 12, wherein the radiant interface detector is at least partially disposed beneath the backside of the substrate support.
15. The method of claim 12, wherein the radiant interface detector further comprises a light selective barrier configured to selectively filter a wavelength corresponding to the laser radiation, and the reflected interference radiation and the reflected control radiation received at the radiation sensor are passed through the light selective barrier.
16. The method of claim 12, wherein the radiant interface detector is an infrared interferometer.
18. The method of claim 12, wherein the substrate support further comprises a lens disposed between the substrate supporting side and the backside, and the lens is transparent to the interference radiation.
19. The method of claim 12, wherein the radiant interface detector is at least partially disposed in the substrate support between the substrate supporting side and the backside.
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February 15, 2019
November 1, 2022
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